MAINT: simplify package metadata handling

Code can be simplified using pyproject_metadata.StandardMetadata also
when we infer the package metadata from meson.build.

mesonpy/__init__.py

@@ -748,20 +748,6 @@ def __init__(  # noqa: C901
         # load pyproject.toml
         pyproject = tomllib.loads(self._source_dir.joinpath('pyproject.toml').read_text())
 
-        # package metadata
-        self._pep621 = 'project' in pyproject:
-        if self.pep621:
-            self._metadata = pyproject_metadata.StandardMetadata.from_pyproject(pyproject, self._source_dir)
-        else:
-            print(
-                '{yellow}{bold}! Using Meson to generate the project metadata '
-                '(no `project` section in pyproject.toml){reset}'.format(**_STYLES)
-            )
-            self._metadata = None
-
-        if self._metadata:
-            self._validate_metadata()
-
         # load meson args from pyproject.toml
         pyproject_config = _validate_pyproject_config(pyproject)
         for key, value in pyproject_config.get('args', {}).items():
@@ -802,9 +788,20 @@ def __init__(  # noqa: C901
         has_valid_build_dir = self._build_dir.joinpath('meson-private', 'coredata.dat').is_file()
         self._configure(reconfigure=has_valid_build_dir and not native_file_mismatch)
 
-        # set version if dynamic (this fetches it from Meson)
-        if self._metadata and 'version' in self._metadata.dynamic:
-            self._metadata.version = self.version
+        # package metadata
+        if 'project' in pyproject:
+            self._metadata = pyproject_metadata.StandardMetadata.from_pyproject(pyproject, self._source_dir)
+        else:
+            self._metadata = pyproject_metadata.StandardMetadata(name=self._meson_name, version=self._meson_version)
+            print(
+                '{yellow}{bold}! Using Meson to generate the project metadata '
+                '(no `project` section in pyproject.toml){reset}'.format(**_STYLES)
+            )
+        self._validate_metadata()
+
+        # set version from meson.build if dynamic
+        if 'version' in self._metadata.dynamic:
+            self._metadata.version = self._meson_version
 
     def _proc(self, *args: str) -> None:
         """Invoke a subprocess."""
@@ -858,8 +855,6 @@ def _configure(self, reconfigure: bool = False) -> None:
     def _validate_metadata(self) -> None:
         """Check the pyproject.toml metadata and see if there are any issues."""
 
-        assert self._metadata
-
         # check for unsupported dynamic fields
         unsupported_dynamic = {
             key for key in self._metadata.dynamic
@@ -991,45 +986,18 @@ def _meson_version(self) -> str:
 
     @property
     def name(self) -> str:
-        """Project name. Specified in pyproject.toml."""
-        name = self._metadata.name if self._metadata else self._meson_name
-        assert isinstance(name, str)
-        return name.replace('-', '_')
+        """Project name."""
+        return self._metadata.name.replace('-', '_')
 
     @property
     def version(self) -> str:
-        """Project version. Either specified in pyproject.toml or meson.build."""
-        if self._metadata and 'version' not in self._metadata.dynamic:
-            version = str(self._metadata.version)
-        else:
-            version = self._meson_version
-        assert isinstance(version, str)
-        return version
+        """Project version."""
+        return str(self._metadata.version)
 
     @cached_property
     def metadata(self) -> bytes:
-        """Project metadata."""
-        # the rest of the keys are only available when using PEP 621 metadata
-        if not self.pep621:
-            data = textwrap.dedent(f'''
-                Metadata-Version: 2.1
-                Name: {self.name}
-                Version: {self.version}
-            ''').strip()
-            return data.encode()
-
-        # re-import pyproject_metadata to raise ModuleNotFoundError if it is really missing
-        import pyproject_metadata  # noqa: F401
-        assert self._metadata
-
-        core_metadata = self._metadata.as_rfc822()
-        # use self.version as the version may be dynamic -- fetched from Meson
-        #
-        # we need to overwrite this field in the RFC822 field as
-        # pyproject_metadata removes 'version' from the dynamic fields when
-        # giving it a value via the dataclass
-        core_metadata.headers['Version'] = [self.version]
-        return bytes(core_metadata)
+        """Project metadata as an RFC822 message."""
+        return bytes(self._metadata.as_rfc822())
 
     @property
     def license_file(self) -> Optional[pathlib.Path]:
@@ -1044,11 +1012,6 @@ def is_pure(self) -> bool:
         """Is the wheel "pure" (architecture independent)?"""
         return bool(self._wheel_builder.is_pure)
 
-    @property
-    def pep621(self) -> bool:
-        """Does the project use PEP 621 metadata?"""
-        return self._pep621
-
     def sdist(self, directory: Path) -> pathlib.Path:
         """Generates a sdist (source distribution) in the specified directory."""
         # generate meson dist file

tests/test_metadata.py

@@ -10,11 +10,11 @@ def test_no_pep621(sdist_library):
     with tarfile.open(sdist_library, 'r:gz') as sdist:
         sdist_pkg_info = sdist.extractfile('library-1.0.0/PKG-INFO').read().decode()
 
-    assert sdist_pkg_info == textwrap.dedent('''
+    assert sdist_pkg_info == textwrap.dedent('''\
         Metadata-Version: 2.1
         Name: library
         Version: 1.0.0
-    ''').strip()
+    ''')
 
 
 def test_pep621(sdist_full_metadata):
@@ -61,10 +61,10 @@ def test_pep621(sdist_full_metadata):
 
 def test_dynamic_version(sdist_dynamic_version):
     with tarfile.open(sdist_dynamic_version, 'r:gz') as sdist:
-        sdist_pkg_info = sdist.extractfile('dynamic_version-1.0.0/PKG-INFO').read().decode().strip()
+        sdist_pkg_info = sdist.extractfile('dynamic_version-1.0.0/PKG-INFO').read().decode()
 
-    assert sdist_pkg_info == textwrap.dedent('''
+    assert sdist_pkg_info == textwrap.dedent('''\
         Metadata-Version: 2.1
         Name: dynamic-version
         Version: 1.0.0
-    ''').strip()
+    ''')